KANDAHAR, Afghanistan - Four Taliban suicide bombers disguised in army uniforms detonated a car bomb and stormed a government office yesterday, killing 13 people. The assault highlighted the increasingly deadly tactics that Taliban militants are learning from Al Qaeda, an expert said.

The multi-pronged raid mirrored an attack in Kabul in February when militants assaulted three government buildings simultaneously, killing 20.

Yesterday's attack on Kandahar's provincial council office killed seven civilians and six police officers, President Hamid Karzai's office said. Ahmad Wali Karzai, the head of the council and President Karzai's brother, said the attack came during a meeting of tribal leaders. He said 17 people were wounded.

The attack began just before noon, when a suicide bomber in a vehicle full of explosives blew himself up at the office gates, opening the way for three other attackers in Afghan Army uniforms and AK-47s to storm the building, Ahmad Wali Karzai said. He told The Associated Press he was the target of the attack; he did not say how he knew he was the target.

General David Petraeus, the top US general in the Mideast, said yesterday that the Taliban and other insurgents are growing stronger and that the US military will fight "relentlessly and aggressively" against extremists in Afghanistan and Pakistan.

Al Qaeda and Pakistani militants are teaching advanced skills to the Taliban, and Al Qaeda operatives are embedding with Taliban forces to "plus-up their capabilities," said Bruce Hoffman, a terrorism expert at Georgetown University.

"So I think overall that this is a reflection of the Afghan Taliban's skill set really being enhanced, both with their symbiotic relationship with jihadi elements across the border in Pakistan and with Al Qaeda."

After the car bomb explosion, three militants wearing suicide vests and carrying rifles entered the Kandahar compound, said Interior Ministry spokesman Zemeri Bashary. Police killed two of the attackers and the third one blew himself up, he said. A fourth bomber died in the car bomb, bringing the overall death toll to at least 17.